Let's Make Robots!

Which rechargeable battery to choose?

Lately I've been a bit more careful about how I spend my money on my robotics projects (wasn’t able to get a summer job this year) and I have notices one big problem: batteries! 


My first robot takes 12 AA! And they dont last all that long before you start noticing differences in performance.

My second one takes a 9V and if you know a bit about batteries you'll know that is a really bad battery to use.


So I would like to replace that 9V with a rechargeable battery, something that gives out 9V to ~15V and wont break the bank.


So any suggestions would help loads! 


The reason I dont search for myself is because I have no clue what I am looking for other than the output.    

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Found the perfect one !


It is the cheapest one yet and all is included! 

To be safe, seperate the electronics and just tie the grounds togather. I have no experience on you processor but presumes it runs on a 3.4v or 5v regulator. Motors take lots of MA or amps. Electronics run on low MA depending how many sensors and LEDs and misc. devices you are using. I have run my boe bot down to 6 volts and it still moved. AA batterys never last long compaired to sub C type witch they use in R/C cars and stuff for a reason. They would be fine for the electronics though. They even have rechargable 9v batterys and small 7.2 v batterys for model helicoptors. My Mini Monster Boe Bot got big and uses 3 seperate batterys and will run about 2 hrs. continious. Of coarse the motor and laser, camera battery go first. Remember when the amps go then the voltage drops.And I=E/R no matter what. Ohms law is very simple and basic. Hope this helps.

I just tested the TheChosenOne with a 7.2V battery pack (from my rc car that I never use) and everuthing lights up okay, but it does the same with an old 9V battery so this doesnt meen much.

The only way to truly test it is to remote controle it with the pc and see if it resets, just one problem, my 15 day trial of bluesoleil just expired so I cant test it. And even better since i cant install the programing sofware i cant event try the bumper program which would also allow me to see if it restarts.


2 of theise might do the job if my bot can live with less than 9V


1 to power the bot, the other to power anything that I would normally attache to the breadbord.


If you can gey by with 8.4V, there are some cheap ones on Ebay has some on sale for 1/2 the price. They have alot to choose from and some chinese places may offer free shipping. 7.2 V is more standard and you could put them in series. I saw a RC battery charger 110v and 12v input with the timer for around $12 a few days ago. They have a hi amp timer mode that can charge batterys in around 15 min. I always use NiCads for my robots or would be broke from the batterys. It is hard to beat Ebay. Futiba and Hitech are good name brands but generics are good too. Look under radio control and hobbys.  It is always good practice to run electronigs seperate from motor controls, especially with more complicatted stuff.  There is a big difference betrwwn amps and MA so AA packs would probally do OK
I might be able to do with 8.4 but i need to know one thing to be sure: when you get a power surge when the battery is geting low which causes your robot to reset, would that be cause by low voltage or low mAh ?

I found this battery pack (http://www.all-battery.com/nicd96v2400mahhighpowerhumpbatterypackforrccarswithtamiyaconnector--new.aspx)

 that looks decent, 9.6V and 2400mAh for only 12$ (without shipping) and this charger (http://www.all-battery.com/smartuniversalchargerfornimhnicdbatterypack7-2v-12v-01020.aspx#) might do it .


What do you guys think ? 

NiMHs are probably the easiest to use. You can probably get free samples of battery charging chips from maxim and make a charger pretty easily.

Does your robot REALLY need such high voltage?

Well, the voltage was a bit of a guess, from the documentation on the chip I use http://www.c-stamp.com/CS110000.htm
 I need 5-24V but from experiance if the voltage of the 9V battey drops bellow 9V the chip will accidently reset due to power surges alot easier. 
Are you running the motors from the same battery? The drain from the motors could drop the voltage too far causing resets. If you had 2 packs you could run a lower voltage. A single 9v for the MCU and higher capacity pack for motors.